NU and FSM have made a strong commitment to the development of shared 2P imaging facilities. FSM has invested approximately $2.2M to purchase equipment, renovate space and hire technical staff for the three existing 2P core facilities. As part of their continuing commitment, FSM has authorized the allocation of an additional $300K for the purchase of instrumentation to create a core for in vivo 2P imaging (Core 4). This was a 'matching'commitment in the original P30 application but the money was given as a good faith gesture in spite of the failure to secure NINDS support. It is worth noting that the $2.5M figure does not reflect the school's investment in new faculty (salaries, lab renovations, start-up costs) with demonstrated expertise in 2P imaging applications (Drs. Grutzendler, Waters, Shepherd, and Osten);this investment exceeds $4M. If one adds in the investment in the last three years in faculty working in dendritic-synaptic physiology and neural stem cell biology (creating the neuroscience community in which these techniques can fluorish), the total NU commitment to this enterprise exceeds $25M. With the support called for in this proposal, we can build on this commitment by improving the operation of the existing cores as well as creating new ones for NINDS funded investigators who need these technologies to advance their research programs but cannot be accommodated at present. NU is prepared to expand their commitment if NINDS takes this step, providing additional space (Cores 5 and 6) and salary support for core staff (Drs. Wokosin, Hockberger and Core 6 staff;see accompanying commitment letters).